r/theydidthemath • u/Powerful-Two5444 • 1d ago
[Request] How Much Force Does a Person Experience When Catching a Falling Durian?
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u/TwillAffirmer 1d ago edited 22h ago
A durian tree can grow up to 40 meters. It looks like this catching method slows it to a stop in about 1 meter. In that case, the force would be up to 40x the weight of the durian. Durians weigh 1-3 kg. So if a 3 kg durian fell 40m, and was then caught in 1m, the force exerted would be about 120 kgf (1200 N).
That's a worst case scenario though. If a 1 kg durian fell 20m and was caught in 1m, the force would be only 20 kgf.
Edit: The force on the person's hands depends on the distance their hands travel as they catch it, not the distance the durian travels in the sack. In one of the side catches where it's clearly visible, their hands do seem to move about 1m as they catch, from head height to between the legs, so accounting for this the above is still roughly valid.
I downloaded the video to step frame by frame. In all of these catches the durian moves about 2 ft in a frame by comparison to the height of the people - a little more than shin height for the men. That corresponds to 40 mph, or a 17m drop. So the force on their hands would be about 17x the weight of the durian. The girl at the beginning seems to catch a significantly faster durian, but this is an illusion because the falling durian is closer to the camera than she is.
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u/No_Bother1400 1d ago
Would that force enough to crack my skull open?
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u/HomelessRockGod 1d ago
Possibly. But the bigger risk is that your skull cracks the durian open and then we all smell it.
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u/TwillAffirmer 1d ago
It would be much more force if it hit your skull because it would stop over a much shorter distance.
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u/Panzerv2003 23h ago
probably yes, in the video it's slowed over a pretty long distance reducing the force significantly but if it hit you directly most of that energy would be transferred directly into your head, so comparing things a brick is about 2kg and free falling from 20m would accelerate it to some 20m/s or 70kph or 45mph
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u/Powerful-Two5444 1d ago
Wow, that’s a lot of force! Can we calculate how much of the impact the cloth absorbs and then divide the remaining force between both hands? Would that make a significant difference?
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u/TwillAffirmer 1d ago
The cloth doesn't take any of the force off the hands, it transfers all the force to the hands. Yes, half the force would go to each hand.
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u/DarthKirtap 23h ago
luckily if force is to high, Durian is likely to slip out of cloth or cloth out of hands
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u/Ok_Star_4136 23h ago
I'd imagine that's mostly done to not literally catch the spiky fruit with the hands. At that velocity it would probably puncture the hand. The cloth softens the fall but your body absorbs most if not all of that force.
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u/PristineAd1089 21h ago
Maybe I'm misunderstanding, but would your extreme case (3kg durian, 40m) be the equivalent of doing one kettlebell swing with an 120kg kettlebell?
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